1. Field of the Invention
The present invention relates to a random number generator, and more particularly, to a low power random bit generator and a random number generator using the random bit generator.
2. Description of the Related Art
As information security becomes increasingly important, random number generators, which produce an encryption key and a decoding key, become more essential for many types of electronic systems.
To be embedded in a mobile system such as a smart card, the random number generator should have a simple configuration and consume little power. In particular, if the random number generator is implemented on a semiconductor chip, the random number generator should be compact.
FIG. 1 is a block diagram of a random number generator using an analog system. The random number generator includes a random bit generator (RBG) 100, a post processor 200, and an output buffer 300.
The RBG 100, which is an analog signal processing unit, generates a predetermined random bit signal by using a noise source.
The post processor 200, which is a digital signal processing unit, receives the random bit signal and performs predetermined digital signal processing on the received random bit signal. As a result of the digital signal processing, the randomness of the random bit is increased. Through digital signal processing, algorithms are digitally processed, such as correction and compression, for the random bit signal.
The random bit signal on which digital processing has been performed is transmitted to the outside through the output buffer 300.
A typical way to generate a random bit signal by using an analog signal is to use white noise that is obtained from a resistor which is not biased at a constant voltage. Since the voltage level of a noise signal is typically extremely low, it is not until the noise signal is amplified by an amplifier with a very high gain that the noise signal can be used.
In general, the amplifier consumes much power, thereby increasing the power consumption of a system and the size of a chip. Moreover, in the amplifier, the power supply rejection ratio (PSRR) is deteriorated due to: a) noise caused by peripheral digital logic circuits operating at high frequencies on a semiconductor chip; b) power supply noise; and c) flicker noise. In other words, the amplifier may output unexpected voltage or current due to various types of noise.
To prevent or reduce as much as possible the influence of the digital circuits operating at high frequencies, the amplifier should be separated from the peripheral circuits. However, the separation of the amplifier from the peripheral circuits cannot be easily implemented and requires a large area. Further, to suppress spike noise from a power supply, a resistor having a large resistance and a capacitor having a large capacitance should be installed on the power supply.